Electrical rectifier



june 30, 1936. p. H- DOWLlNG 2,046,153@

ELECTRICAL RECTIFIER Filed Feb. 14, 1935 l INVENTOR Phzlip H.D0wlz2g BY@2x 'E5 HIS ATTORNEY 20 formed thereon.

Patented June 30, 1936 UNITED STATES PATENT OFFICE ELECTRICAL BECTIFIERApplication February 14, 1935, Serial No. 6,527

10 Claims.

My invention relates to electrical rectiers, that is, to devicessuitable for changing alternating currents into unidirectional currents.More specifically, my invention relates to an im provement in thewell-known copper oxide rectier which is described in Patent No. 1,640,-335, granted August 23, 1927, to Lars O. Grondahl.

I will describe one iorm of electrical rectier embodying my invention,and will then point out the novel features thereof in claims.

' The accompanying drawing is a vertical, longitudinal, sectional viewshowing one form of electrical rectier embodying my invention.

Referring to the drawing, the rectier comprises a plurality of etricunits each designated by the reference character A, and each comprisinga plate l oi a metal such as copper having a coating 2 of a compound ofthe metal For example. the coating 2 may be cuprous oxide. Asymmetricumts of the type described exhibit the characteristics of oftering ahigher resistance to current which tends to now from the copper to theoxide than to 25 current which tends to now in the opposite directionthrough the unit. A plurality oi.' the asymmetric units A may beassembled on a suitable support, here shown as a bolt D which passesthrough suitable openings in the units, but which 3o is separated fromthe units by av sleeve 3 of insulating material. Adjacent the coating 2of cuprous oxide oi each unit A is placed an electrode B of anon-fusible, non-oxidizable, nonductile conducting material such, forexample, as carbon. The units A are assembled on the bolt D in themanner shown in the drawing, that is, with the carbon electrode Binterposed between and making electrical contact with the cuprous oxidecoating ot one unit and the copper of the 40 next unit. vI have foundthat contact between the cuprous oxide coating oi' the units A and theelectrodes B may be improved, either by rubbing iinely divided carboninto the outer surface of the cuprous oxide, or by painting such surface45 with a colloidal emulsion of carbon in water. Adjacent and in contactwith the copper of the left-hand unit A is placed a washer l of a metalsuch as steel. Adjacent and in contact with the right-hand carbonelectrode B is placed a ter-- units A and electrodes B in contact witheach other, I have provided two steel spring washers 4E and 4Funderneath the head of the bolt D and the nut 8, respectively, so thatwhen the nut 8 is threaded on the bolt D, the whole is 5 clamped tightlytogether. In order to insulate the nut 8 from the terminal plate C, Ihave provided an insulating washer 6, and in order to protect the washer6 from damage by the spring washer 4F, I have interposed a dat steelwasher 1G 5 between the spring washer 4F and the insulating washer 6.

The assembled rectifier may be connected in an electrical circuit in anysuitable manner, not shown in the drawing. For example, the con- 15ductors to the circuit may be attached to the terminal plate C and tothe steel washer l which may be considered as the other terminal of therectifier. In suche. circuit the current will be comparatively free toiiow from the terminal plate C to washer 1 but will be almost entirelyprevented flowing from the washer l to the terminal plate C.

Although I have shown only one form of combination of rectiiying unitsemploying my invention, it is understood that other varieties ofcombinations of rectifying units may be made. Since such othercombinations are well known to those skilled in the art, no detaileddescription is being made herein.

One object oi' my invention is to provide increased protection againstthe possibility of breakdown in the high resistance direction, that is,from the copper to the oxide. Another object of my invention is toprovide greater protection against the possibility of an increase inresistance in the low resistance direction, that is from the oxide tothe copper. A still further purpose of my invention is to provideincreased area of contact between the electrodes and the 40 adjacentrectifying units.

Since carbon is not fusible, except at extremely high temperatures,there is little possibility of contact between the copper o! arectifying unit and its associated electrode of carbon even if the unitis subjected to voltage suicently high to puncture the oxide coating ofsuch unit. Inasmuch as carbon does not oxidize at ordinary temperature,the carbon electrodes will maintain a substantially constant contactresistance over a long period o! time. Furthermore, since carbon willnot flow under pressure and the edges of the carbon electrodes arecomparatively clean and i'ree from shreds, the electrodes may besubstantially the same size as the rectifying units, and there'will belittle probability of short circuiting the rectifier at the edge.

From the foregoing description it will be seen that I have provided animprovement in the construction of the well-known copper oxide rectiiierwhich insures increased reliability and eillciency. l

vAlthough I have herein shown and described only one. form of electricalrectier embodying my invention, it is understood that various changesand modifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described myl invention, what I claim is: I

l. A rectifier comprising an asymmetric unit, a carbon coating incontact with said unit. and' a carbon electrode in contact with saidcoating.

2: A rectier comprising an asymmetric unit, a colloidal emulsion ofcarbon applied to said unit, and a carbon electrode in contact with saidcolloidal emulsion.

3. A. rectiiier comprising an asymmetric unit, n

iinely divided carbon in contact with said unit, and a carbon electrodein contact with said finely divided carbon.

li. A rectifier comprising an asymmetric unitA composed oi' copper andan oxide thereof, a cai'u bon coating in contact with said omde, and acarbon electrode in contact-with said coating.

5. In combination, a metal having an electroconductive compound of themetal formed thereon, said combination constituting in and of itself aunidirectional current carrying device, finely divided carbon applied tothe free surface of said compound, and a carbon electrode pressed intointimate electrical contact with said compound.

6. In combination, a metal and an electro-comductive compound inintimate and permanent electrical contact with said metal, saidcombination constituting in and of itself a unidirectional currentcarrying device, a carbon coating applied to said compound, a carbonelectrode in contact with said coating and means for pressing saidelectrode against said coating with considerable' force.

'1.v In combination, a bolt, a plurality. of imits mounted thereon andeach comprising the combination of a metal with a compound of the metalformed thereon, such combination constituting in and of itself aunidirectional current carrying device, finely divided carbon appliedtothe free surface of the compound in each unit, a carbon electrode inengagement with the free surface of the compound in each unit, and a'nut for clamping said units together on said bolt.

8. In combination, a bolt, a plurality of units mounted thereon and eachcomprising the combination of copper with cuprous oxide formed thereonand integral therewith, such combination constituting in and of itself aunidirectional current carrying device, ilnely divided carbon applied tothe free surface of the compound in each unit, a carbon electrode inengagement with the free surfaceof the compound in each unit, and a nutfor clamping said units together on said bolt.

9. In a rectifying device, a coppertplate having a layer of cuprousoxide integrally formed over substantially the entire surface of oneside` of said plate, said copper plate and oxide layer' metric unitseachhaving finely divided carbon applied thereto, a pllnality of carbonelectrodes connecting said units with each other, one terminal incontact with one of said units for connecting said rectiiler to acircuit, and another terminal in contact with one of said electrodes:for also connecting said rectifier to such circuit. f PHILIP H.BOWLING.

